Feedhorn s kruhovou polarizací pro parabolické antény

Feed-horn with circular
polarization for parabolic
dish
Zdenek SAMEK – OK 1 DFC
Why septum transformer ?
z
z
z
z
z
z
z
Necessary use circular polarization over 1 GHz
Possibility use feed for LCP and RCP without 90° hybrid
and TX-RX switching
Saving 1,5 dB on the RX and TX site
Saving money for expenses High power relay.
Advantage that between TX and RX sites are loss more
then 26 dB
Good impedance adaptation both TX and RX ports
Very easy possible set up high SWR
Electric diagram of septum
VE 4 MA – W 2 IMU – system
Septum-feed – OK 1 DFC
h
v
RX port
Hybrid
Relay for
high power
TX port
CX520 relay
50R
30W
Preamp
Preamp
50R
1W
RX
TX
RX
TX
How is it working ?
L
TX
R
RX
TX
V
RCP
H
RX
Driving of transformer
Vertical part of electromagnetic wave
1
2
3
1. Four-square wave guide on the feed input
2. Septum transformer
3. Rectangular wave guide in RX – TX part, very close to by
connector
Driving of transformer
Horizontal part of electromagnetic wave
1
2
1. Four-square wave guide on the input
2. Septum transformer
3. Rectangular part of RX and TX wave guide
3
Parts of feed
C
B
A
RX
TX
D1 – D2
RX – connector for receiving cable
TX – connector for transmitting cable
D1 – D2 – compensation capacitors for set up SWR
A – Rectangular parts RX - TX
B – Transformer
C – For-square output wave guide
Circularity of polarization
0 dB
x
-1,6dB
-Diagram of circularity
y
-Theoretical maximum of
discircurality is – 1,1 dB
-With not correctly calculate
septum transformer will be
diagram as a „cake“
Measurement diagram in unreflecting chamber TX
Smě rové c harakte ris tiky ozařovač e Se ptum 2,3 GHz
-20
-25
-30
[dBm ]
-35
-40
-45
-50
-55
-60
0
30
60
90
120
150
180
210
240
270
300
[°]
P kone ktor, rovina
P kone ktor, rovina
P kone ktor, rovina
P kone ktor, rovina
kolm á na kone ktory, vys íla ná Ve rt. pola riza ce , 2,3 GHz [dBm ]
rovnobě žná s kone ktory, vys íla ná Ve rt. pola riza ce , 2,3 GHz, přívodní ka be l na 270 s t. [dBm ]
rovnobě žná s kone ktory, vys íla ná Hor. pola riza ce , 2,3 GHz, přívodní ka be l na 270 s t. [dBm ]
kolm á na kone ktory, vys íla ná Hor. pola riza ce , 2,3 GHz [dBm ]
330
360
Measurement diagram in unreflecting chamber RX
S mě ro vé charakte ristiky oza řova če S e ptum 2,3 GHz
-20
-25
-30
[dBm]
-35
-40
-45
-50
-55
-60
0
30
60
L kone ktor, rovina
L kone ktor, rovina
L kone ktor, rovina
L kone ktor, rovina
90
120
150
180
210
240
270
300
[°]
kolm á na kone ktory, vys íla ná Ve rt. pola riza ce , 2,3 GHz [dBm ]
rovnobě žná s kone ktory, vys íla ná Ve rt. pola riza ce , 2,3 GHz, přívodní ka be l na 90 s t.
rovnobě žná s kone ktory, vys íla ná Hor. pola riza ce , 2,3 GHz, přívodní ka be l na 90 s t.
kolm á na kone ktory, vys íla ná Hor. pola riza ce , 2,3 GHz [dBm ]
330
[dBm ]
[dBm ]
360
Comments
z
z
z
z
z
z
We saw that circularity is absolutely perfect
Diagram was done for 2,3 GHz feed
Measurement condition-unreflecting chamber of Electrotechnician University Praha
Radiation angel 130° for –10 dB
Practical use for dish with 0.35 F/D
For other F/D is possible use with choking collar like
VE4MA feed. Practical solution has Franta OK1CA
Practical calculation
Comments
z
z
z
z
z
z
We saw that calculation is in Excel very comfortable
All dimensions are in mm
Material for feed is Aluminum or Cooper sheet
Do not use bras, problem with freeze
For frequency up to 2.3 GHz accuracy up to 0,5mm
Higher frequency up to 0,1mm
Types of septum transformer
1.
2.
Sloping septum
Chen and Tsandoulas septum
- isolation RX-TX 25 dB max.
- isolation RX-TX up to 27,5 dB
max.
- discircurality 2 – 3 dB
- easy for producing
- Maximum of discircurality 1,1
dB
- Circularity for very wide
frequency range +,- 10% of
calculation frequency
Practical solution of feed
Feed for 1296 MHz – practical solution
Assembly of on the RX port for 1296 MHz
Assembly of feed – look to compensation capacity screw.
Application of feed by OK 1 UWA for 1296 MHz
Feed with funnel by OK 1 CA for 2320 MHz and Cassegrain
mirror
Thank you for your attention –
GL and 73 !
OK 1 DFC